21253431420 has 288 divisors, whose sum is σ = 71080027200. Its totient is φ = 5108133888.

The previous prime is 21253431403. The next prime is 21253431431. The reversal of 21253431420 is 2413435212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 50723971 + ... + 50724389.

It is an arithmetic number, because the mean of its divisors is an integer number (246805650).

Almost surely, 2^21253431420 is an apocalyptic number.

21253431420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21253431420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35540013600).

21253431420 is an abundant number, since it is smaller than the sum of its proper divisors (49826595780).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21253431420 is a wasteful number, since it uses less digits than its factorization.

21253431420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 909 (or 904 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 27.

Adding to 21253431420 its reverse (2413435212), we get a palindrome (23666866632).

The spelling of 21253431420 in words is "twenty-one billion, two hundred fifty-three million, four hundred thirty-one thousand, four hundred twenty".